Quiz 6 - Fall 2004
Multiple Choice
Identify the letter of the choice that best completes the statement or answers the question.
__C__ 1. The oldest rocks found on Earth are about _______________ years old.
a. 10 billion
b. 5.3 billion
c. 4.6 billion
d. 3.9 billion
e. 6.2 million
__A__ 2. Once a terrestrial planet had formed from a large number of planetesimals, heat from _______________ could
have melted it and allowed it to differentiate into a dense metallic core and a lower density crust.
a. radioactive decay
b. the sun
c. volcanic eruptions
d. tidal forces
e. impacts of small meteorites
__B__ 3. The condensation sequence suggests that _______________ should condense closest to the sun.
a. Jovian planets
b. metals and metal oxides
c. silicates
d. ices of water, methane, and ammonia
e. low density materials
__A__ 4. Which one of the following objects is most like the planetesimals that formed in the solar nebular?
a. asteroids
b. Earth
c. Saturn
d. Venus
e. the sun
__B__ 5. The large planetesimals would have grown faster than the smaller planetesimals because
a. they were moving faster in their orbits than the smaller planetesimals.
b. their stronger gravity would pull in more material.
c. there was more material located near them that could be accreted.
d. the smaller planetesimals were covered by a layer of material that was lost during
collisions.
e. all of the above
__D__ 6. If a star is found with five planets orbiting it, which of the planets would be expected to have the greatest
uncompressed density if the system was formed by a process like that described in the solar nebula theory?
a. The one farthest from the star.
b. The one with the greatest mass.
c. The one with the greatest radius.
d. The one closest to the star.
e. The one that has liquid water on its surface.
__B__ 7. The uncompressed mass of a planet in our solar system is greatest for the
a. Jovian planets.
b. planets closest to the sun.
c. planets furthest from the sun.
d. planets with the largest mass.
e. planet with the largest radius.
__C__ 8. What are the three “common” substances that are believed to be important in planet formation?
a. Solid, liquid, and gaseous hydrogen.
b. Electromagnetic radiation, electrical discharges (e.g., lightning), water.
c. Rock, ices, and gas.
d. Hydrogen, helium, and neon gases.
__D__ 9. According to modern theories, the most significant difference between the formation of the terrestrial and the
large, outer planets is that
a. the terrestrial planets formed close to the Sun where there was an abundance of rock but
no ice, whereas the outer planets formed far from the Sun where there was an abundance
of hydrogen and ice but no rocky material.
b. both formed by accretion of rocky and icy planetesimals, but the terrestrial planets were
close enough to the Sun that almost all of the ices escaped back to space after the planets
formed.
c. the terrestrial planets formed by accretion of planetesimals, whereas the outer planets
formed by direct condensation of gas from the solar nebula.
d. both formed by accretion of planetesimals but the outer planets became massive enough to
also pull gas onto them directly from the solar nebula.
__C__ 10. The diagram below illustrates the radioactive decay of Potassium (40K), which has a half-life of 1.3 billion years.
If a lunar rock is found that currently contains 5 grams of 40K, and it is determined that the sample contained 20
grams when it was formed, how old is the lunar rock?
a. 6.5 billion years
b. 19.5 billion years
c. 2.6 billion years
d. 3.9 billion years
e. 4.6 billion years